I have a couple Exo's in that size - love 'em. Mine house a group of Bothriechis lateralis.
I modified, grouted and sealed the styro backgrounds. Modification involved great-stuffing some pots and perches (including embedded stubs of branches at various heights) onto the backgrounds. Looks and works awesome (my bromeliads are thriving). I sealed with spray-on clear expoxy, like you see in motorcycle shops. (I let it dry for about a month, and rinsed it a lot after the first week drying).
Substrate is chunky coir. I set these cages up in a hurry (story of my life) so didn't drill the tanks or even make a false bottom or other drainage layer - just threw in the substrate, and stuck (de-potted) plants into it. Usually I like at least a false bottom. However I have not missed it here (except I can't do a water feature...bummer).
Survival of plants has been a cold-hearted Darwinian experiment. Winners thus far include Ficus elastica, Pepperomia sp., Dracaena sp., Philodendron sp., Neoregelia sp., Tradescantia fluminensis, and Aglaonema modestum.
Losers have included Dieffenbachia sp., Calathea sp., and a couple of very herbaceous specimens of unknown species.
The Exos are hooded - I have 2 CFs per hood (there's space for 3 but that makes it too hot for this montane species).
I hand-mist daily. I keep a variety of arboreal vipers and only the lateralis seem perpetually happy to get a drink. Others (e.g. A. chloroechis) seem like they're fine with 2x a week or so. This variable schedule will affect what plants live or die. E.g. Schefflera are OK with the chlorechis - 2x/week - but get (terminal) fungal diseases when misted daily. (Actually Atheris seem to not do well with a lot of misting too...but that's another topic, sorry).
I've never kept arboreal boids so can't comment on what plants will work with whatever misting schedule they require. The Exos are good for snake lungs, because airflow is good, particularly with the drafting introduced by an overhead heat/light source. I think the crack between the doors, and the vent below them, is key here. I don't know arboreal boids at all, but in vipers the susceptibility to lung-crud (lethal!) varies A LOT, in about this order in my experience (least-most): "Trimeresurus", Bothriechis, Atheris, Tropidolaemus.
I'd be curious what people have to say about boids' susceptibility.
cheers,
Jimi